Cutting tools, systems and methods for navigated bone alterations

ABSTRACT

Cutting tools, systems and methods for navigated procedures are provided. A cutting tool (e.g. oscillating blade, etc.) for a power tool has an optically trackable feature in a defined positional relationship relative to a cutting feature of the cutting tool. The trackable feature may include reflective material applied to a surface (e.g. a recessed blade surface). The trackable feature is be imaged by a camera integral with or attached to the power tool and provided to a computing unit of a navigation system to determine a relative pose of the cutting feature and camera. The camera may also track a patient&#39;s bone such that the computing unit may determine a relative position of the bone and camera. The unit then computes a relative pose of the cutting feature with respect to the patient&#39;s bone and provides same for determining display information and/or to a robotic controller for procedural control.

CROSS REFERENCE

This application claims the benefit of U.S. Provisional Application No.62/489,037, filed Apr. 24, 2017, the contents of which are incorporatedherein by reference.

FIELD

This disclosure relates to cutting tools and computer assistednavigation for a procedure and more particularly to cutting tools,systems and methods for navigated bone alterations such as a bone cut.

BACKGROUND

In many types of surgery, a surgeon performs a bone cut to a patient'sbone to achieve one or more surgical goals. Total Knee Arthroplasty(TKA) is presented as an exemplary surgical procedure, in which a distalfemur and proximal tibia are cut using an oscillating saw to prepare thebones to receive respective implants. In this example, the cutting toolis an oscillating saw blade 100 (as shown in FIG. 1), which may be asingle-use, pre-sterilized component, comprising a cutting feature 102(e.g. saw teeth) and an attachment mechanism 104 providing an interfaceto couple to a power tool. The cutting feature is typically defined byone or more surfaces of the cutting tool, often located at or along anoutermost surface of the cutting tool. The surfaces may be located at anend of the cutting tool such as in the oscillating saw blade 100 asshown but not necessarily so. An assembly comprising a power tool 200and an oscillating saw blade 100 is illustrated in FIG. 2. The powertool provides the mechanical actuation to move the oscillating saw).

Positional accuracy of cuts to the patient's bone (e.g. relative toanatomical planes, weight bearing axes, other cuts) may be important toa successful surgical outcome. For example, in TKA, having awell-balanced, well-aligned knee is dependent on implant positioning,which is dictated primarily on the position of the cuts to the patient'sfemur and tibia. These cuts may be guided by the positioning of cuttingjigs relative to the anatomy.

SUMMARY

Cutting tools, systems and methods for navigated procedures areprovided. A cutting tool (e.g. oscillating blade, etc.) for a power toolhas an optically trackable feature in a defined positional relationshiprelative to a cutting feature of the cutting tool. The trackable featuremay include reflective material applied to a surface (e.g. a recessedblade surface). The trackable feature is be imaged by a camera integralwith or attached to the power tool and provided to a computing unit of anavigation system to determine a relative pose of the cutting featureand camera. The camera may also track a patient's bone such that thecomputing unit may determine a relative position of the bone and camera.The unit then computes a relative pose of the cutting feature withrespect to the patient's bone and provides the relative pose of thecutting feature with respect to the patient's bone for display or otherprocedural control, such as to a robotic controller.

In one aspect there is provided a cutting tool comprising: a cuttingfeature; an optically trackable feature, wherein: the opticallytrackable feature is detectable by a camera; and the optically trackablefeature has a defined positional relationship with the cutting feature;and an interface to couple the cutting tool to a power tool.

The optically trackable feature may be a pattern of reflective materialapplied to a surface of the cutting tool. The cutting tool may be anoscillating saw blade, and the pattern of reflective material applied toa recessed surface of the oscillating saw blade.

The cutting tool may be an oscillating saw blade and comprise twoidentical optically trackable feature (e.g. a first optically trackablefeature and a second optically trackable feature). The first opticallytrackable feature and second optically trackable feature may appearidentically on opposite sides of the oscillating saw blade.

The cutting tool may have a primary plane or axis, and the definedpositional relationship is based on the optically trackable featurelying along the primary plane or axis.

The cutting tool may be one of: an oscillating saw blade, areciprocating saw blade, a drill bit, a high speed burr, and a rasp.

There is provided a system to navigate a bone cut of a patient's bonecomprising: a cutting tool comprising: a cutting feature; an opticallytrackable feature, wherein: the optically trackable feature isdetectable by a camera; and the optically trackable feature has adefined positional relationship with the cutting feature; and aninterface to couple the cutting tool to a power tool; and a computingunit communicatively coupled to the camera, the computing unitcomprising at least one processing unit and a storage device storinginstructions, which when executed by the at least one processing unit,configure the computing unit to: receive a first image from the camerawhen: the cutting tool is in a nominal stationary position, the camerais attached to the power tool, and a field of view of the cameraincludes the optically trackable feature; measure a relative pose of thecamera and the optically trackable feature based on the first image;compute a relative pose of the camera and the cutting feature based onthe defined positional relationship; receive a second image from thecamera when: a target associated with a patient's bone is within thefield of view of the camera; measure a relative pose of the camera andthe target based on the second image; compute a relative pose of thecutting feature with respect to the patient's bone based on the relativepose of the camera and the target associated with the patient's bone andthe relative pose of the camera and the cutting feature; and provide therelative pose of the cutting feature with respect to the patient's bonefor determining display information and/or to a robotic controller forcontrolling a procedure.

The instructions may configure the computing unit to perform aregistration of a patient's anatomical axes to the target, and to usethe registration of the patient's anatomical axes to the target tocompute the relative pose of the cutting feature with respect to thepatient's bone.

The camera may be integrated into the power tool.

The patient's bone may be a femur, the bone cut may be a distal femoralcut in a TKA. The display information may include at least one of: avarus/valgus angle; a flexion/extension angle, a lateral resectionlevel, and a medial resection level with respect to the femur. Theinstructions may configure the computing unit to: receive a third imagefrom the camera when a second target associated with a patient's tibiais within the field of view of the camera; measure a relative pose ofthe camera and the second target based on the third image; compute arelative pose of the cutting feature with respect to the patient's tibiabased on the relative pose of the camera and the second target and therelative pose of the camera and the cutting feature; and compute andprovide for display at least one of: a varus/valgus angle, aflexion/extension angle, a lateral resection level, and a medialresection level, based on the relative pose of the cutting feature withrespect to the patient's tibia.

The instructions may configure the computing unit to: continuouslyreceive image data of the target from the camera comprising additionalimages, the target attached to the patient's bone; continuously measurea relative pose of the camera and the target based on the additionalimages; continuously compute a relative pose of the cutting feature withrespect to the patient's bone based on the relative pose of the cameraand the target associated with the patient's bone and the relative poseof the camera and the cutting feature; and continuously provide therelative pose of the cutting feature with respect to the patient's boneto determine display information for real-time display and/or to arobotic controller for controlling a procedure.

There is provided a computer implemented method to navigate a bone cutof a patient's bone using a cutting tool comprising: a cutting feature;an optically trackable feature, wherein: the optically trackable featureis detectable by a camera; and the optically trackable feature has adefined positional relationship with the cutting feature; and aninterface to couple the cutting tool to a power tool. The methodcomprises: receiving, at a computing unit, a first image from the camerawhen: the cutting tool is in a nominal stationary position, the camerais attached to the power tool, the camera is coupled to the computingunit, and a field of view of the camera includes the optically trackablefeature; measuring, by the computing unit, a relative pose of the cameraand the optically trackable feature based on the first image; computing,by the computing unit, a relative pose of the camera and the cuttingfeature based on the defined positional relationship; receiving, by thecomputing unit, a second image from the camera when: a target associatedwith a patient's bone is within the field of view of the camera;measuring, by the computing unit, a relative pose of the camera and thetarget based on the second image; computing, by the computing unit, arelative pose of the cutting feature with respect to the patient's bonebased on the relative pose of the camera and the target associated withthe patient's bone and the relative pose of the camera and the cuttingfeature; and providing, by the computing unit, the relative pose of thecutting feature with respect to the patient's bone to determine displayinformation for display and/or to a robotic controller for controlling aprocedure.

The method may comprise performing, by the computing unit, aregistration of a patient's anatomical axes to the target, and using theregistration of the patient's anatomical axes to the target to computethe relative pose of the cutting feature with respect to the patient'sbone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a representative oscillating saw blade fora power tool according to the prior art.

FIG. 2 is an illustration of a power tool with an oscillating saw bladeaccording to the prior art.

FIG. 3 is an illustration of selected components of a computer assistedsurgical navigation system, showing an example configuration for a totalknee arthroplasty.

FIG. 4 is an illustration of selected components of a computer assistedsurgical navigation system, according to the teachings herein, showingan example configuration for a total knee arthroplasty.

FIG. 5 is an illustration of an oscillating blade having an exampletarget according to the teachings herein.

FIG. 6 is an illustration of a power tool and a camera mounted theretoof FIG. 4 with the oscillating blade of FIG. 5, according to theteachings herein.

FIG. 7 is an illustration of a representative image from the camera ofFIG. 6.

FIG. 8 is a cross-section of an oscillating blade having opticallytrackable features on two sides, according to the teachings herein.

FIGS. 9-11 are flowcharts showing respective operations of a computingunit of a computer assisted surgical navigation system.

DESCRIPTION

Systems for providing intra-operative navigation aim to provide pose(position and orientation) information to a surgeon or robotic system toachieve positional accuracy in surgery (e.g. for implant placement, bonycuts). One such system 300 is illustrated in FIG. 3. FIG. 3 showstargets 302 respectively attached to a femur 304, a tibia 306 and afemur cutting jig 314. The femur 304 and tibia 306, shown on anoperating table 316 are representative only where only a portion of sameare normally exposed for a TKA.

A camera 310 having a field of view (FOV) 308 may be communicativelycoupled (e.g. via wire 313) to a computing unit 301 (e.g. a laptop orother computing unit) for further processing image data from the camera310 to generate pose measurements of the targets 302 relative to thecamera 310. The computing unit 301 generates display data based on posedata, usually following a registration process, and provides the displaydata to a display device (e.g. a display monitor or a display screen 303of the laptop) viewable by a surgeon or other human operator (e.g. 312).Camera 310 may provide image data to the computing unit 301 continuously(e.g. in the form of a video feed or stream of images). The computingunit 301 may process the images continuously and provide display datafor viewing in real-time. An example of a computer assisted surgicalnavigation system having a handheld camera is further described in U.S.Patent Application Publication U.S. 2016/0128783 A1, published May 12,2016 assigned to the present applicant, which is incorporated herein byreference.

The term “pose” may mean a pose in up to 6 degrees of freedom (i.e. 3degrees of freedom for orientation and 3 degrees of freedom fortranslational position). Pose may be in less than 6 degrees of freedom,depending on the context. For example, the pose of a circular disk maybe fully described in 5 degrees of freedom, since orientation about anaxis passing perpendicularly through the center of the disk would not berequired to describe the pose of the disk.

A computer assisted surgical navigation system is described herein foraltering (e.g. cutting) a patient's anatomy (e.g. bone) in which acamera is attached to the power tool, and aimed such that its field ofview encompasses a location of the cutting tool. Furthermore, when thecamera is attached to the power tool, and the cutting tool isapproximately lined up with a desired cut (approximately meaning easilyachievable by eye ball judgment, e.g. within +/−20 degrees or +/−10 cm),the camera's field of view may include a target associated with (e.g.attached to) the patient's anatomy. FIG. 4 is an illustration ofselected components of a computer assisted surgical navigation system400, according to the teachings herein, showing an example configurationfor a total knee arthroplasty In FIG. 4, a femur 304 with a target 302is shown, including a desired cut plane 402. A camera 310 is attached toa power tool 200 via a camera attachment (e.g. clamp 404), and the FOV308 includes target 302 attached to the femur 304 and the cutting tool(e.g. oscillating saw blade 100), when the cutting tool is approximatelyaligned with the desired cut plane 402 (i.e. the oscillating saw blade100 of the power tool 200 is shown to be approximately 20 degrees fromthe desired cut plane 402).

The cutting tool may include an optically trackable feature, such thatwhen in the FOV 308, the camera 310 may generate optical measurements ofthe cutting tool, provide the optical measurements to the computing unit301, and the computing unit 301 may calculate the pose of the cuttingtool with respect to the camera 310.

The optically trackable feature may be a known or defined pattern on thecutting tool. For example, a checkerboard pattern, a series of circles,etc. The pattern may be implemented via ink, dye, anodization,application of reflective and/or coloured material, etc. The opticallytrackable feature may inherently define the pose of the cutting tool.For example, an oscillating saw blade provides a planar cut. Theoptically trackable feature may define the same plane as the cuttingplane (e.g. offset for the thickness of the cutting tool).

FIG. 5 illustrates an oscillating saw blade 500 having a cutting feature502 and a surface 504 with an optically trackable feature 506 (in thiscase, a checkerboard pattern that is co-planar with the cutting plane,and aligned with opposing edges 508A and 508B of oscillating blade 500).

FIG. 6 is an illustration of power tool 200 and camera 310 mountedthereto as in FIG. 4 with oscillating blade 500 of FIG. 5, according tothe teachings herein. FIG. 6 shows the cutting tool having opticallytrackable feature 506 within FOV 308 of camera 310.

FIG. 7 illustrates a representative image 700 captured by camera 310,when camera 310 is attached to power tool 200 with oscillating blade 500(cutting tool) comprising optically trackable feature 506 (e.g. attachedthereto). Optical signals of optically trackable feature 506 arecaptured in image 700. Image 700 may be processed using image processingtechniques such as edge detection, thresholding, segmentation,filtering, etc., to calculate a pose of optically trackable feature 506with respect to camera 310.

Computing unit 301 receives optical signals from camera 310 of opticallytrackable feature 506, and computes the pose of the cutting tool (e.g.oscillating blade 500). Computing unit 301 may rely on a known ordefined relationship between optically trackable feature 506 and cuttingfeature 502 (e.g. a certain pattern is applied during the manufacturingof the cutting tools, the pattern having a defined positionalrelationship with cutting feature 502, and computing unit 301 accessesthis defined positional relationship). Based on the known or definedpositional relationship between optically trackable feature 506 andcutting feature 502, and further based on the measured pose of opticallytrackable feature 506, computing unit may compute a relative posebetween camera 310 and cutting feature 502. Before a bone (e.g. femur304) is cut, the relative pose between camera 310 and cutting feature502 may be computed and stored in memory.

When carrying out an alteration to a patient's anatomy, an operator(human or robot) may bring the cutting tool into approximate alignmentwith the desired cut plane 402. When approximately aligned, camera 310is able to detect optical signals of a target 302 associated with theanatomy. The relative pose of target 302 and camera 310 may be computedby computing unit 301 in communication with camera 310. Computing unit301 may compute and provide for display or further processing therelative pose of cutting feature 502 and the patient's anatomy (e.g.femur 304) based on the relative pose of camera 310 and target 302, andthe relative pose of camera 310 and cutting feature 502 (accessible incomputer memory). Computing unit 301 may utilize mathematical operationsor libraries for spatial transformations when computing relative poses.

Camera 310 may be attached to power tool 200 by any feasible/convenientconfiguration, wherein the attachment provides the appropriate FOV fordetecting optically trackable feature 506 of the cutting tool, as wellas target 302 associated with the anatomy, and maintains rigidattachment for the measurement of optical signals of optically trackablefeature 506 through pose measurement of cutting feature 502 with respectto camera 310 and/or anatomy. For example, camera 310 may be providedseparately from power tool 200, and may be attachable via a clamp (e.g.404). Other camera attachment configurations may include a snap fit,friction fit, magnetic or other mounting, etc. Alternatively, power tool200 may have an integrated camera.

If the rigid positional relationship between camera 310 and power tool200 is compromised, or suspected to be compromised for any reason,computing unit 301 may execute a re-registration of cutting feature 502and camera 310 by repeating the associated steps.

The cutting tool preferably provides an optically trackable feature 506(or features) viewable to camera 310 when attached to power tool 200from a wide variety of angles and/or configurations. For example, wherethe cutting tool is a drill bit, circumferential markings may be appliedto the drill bit, viewable regardless of the rotation of the drill bit.In another example, an oscillating saw blade has two sides, and mayprovide optically trackable features (identical markings) on both sides,such that a user can install the saw blade onto the power tool on eitherside. FIG. 8 is a cross-section of an oscillating blade 800 havingoptically trackable features 802 on two sides.

In some applications, the cutting tool may be mechanically constrainedwhen in use. For example, in TKA, an oscillating saw blade is typicallytightly constrained within a slot of a cutting jig for example toperform a distal femoral cut or a proximal tibial cut. The opticallytrackable feature may sit proud of its surface (e.g. where a reflectivesticker is adhered to a saw blade). The cutting tool may provide arecessed surface such that a proud optically trackable feature does notinterfere with any mechanical constraints (such as a cutting slot)during use. This is illustrated in FIG. 8, where the optically trackablefeatures 802 are recessed below the outermost surfaces 804 of thecutting tool.

A power tool may have two modes: one in which the cutting tool moveswhile in use (e.g. a drill rotates, an oscillating saw bladeoscillates), and one in which the cutting tool is stationary, and in anominal position. While moving it may not be practical to measureoptical signals from the optically trackable feature. Therefore, it maybe more practical to measure optical signals from the opticallytrackable feature while the cutting tool is in a nominal stationaryposition.

Application to TKA

The system may be applied to TKA. A camera (e.g. an infrared camera thatemits infrared illumination to be reflected back to the camera) may beattached to a power tool for coupling with an oscillating saw blade usedfor cutting a distal femur and proximal tibia. The oscillating saw bladeprovides an optically trackable feature (e.g. a pattern of reflectivematerial, such as a retroreflective material, to reflect the infraredillumination, applied to the main surface of the saw oscillating blade,the pattern being planar in the same primary plane as the oscillatingsaw blade, and aligned with the side edges (i.e. neither the cutting,nor attachment edges) of the oscillating saw blade).

An image capture may be invoked automatically by a computing unit, or inresponse to user input (e.g. via a button press from a button located onthe camera or other input device). The computing unit may receive thecaptured image, where the image includes optical signals of theoptically trackable feature. The computing unit may then compute a poseof the optically trackable feature with respect to the camera. Thecomputing unit may then compute a pose of the cutting feature of thecutting blade with respect to the camera by equating the cutting feature(i.e. the cutting plane) with the plane of the optically trackablefeature.

A surgeon may attach a femur target to the patient's femur, e.g. viabone screws. The computing unit may execute instructions to receiveoptical measurements for intra-operative navigation and perform aregistration of a patient's anatomical axes to the target, e.g.clinically relevant anatomical axes of the femur to the femur target.The surgeon may provide inputs to the method of generating registrationdata in accordance with the computing unit instructions, for example, byidentifying anatomical landmarks using a navigated probe.

When the distal femur is ready to be cut (i.e. after exposure and softtissue dissection and release), when the power tool assembly (i.e. thecamera rigidly attached to the power tool comprising the oscillating sawblade with optically trackable features attached thereto) is broughtinto approximate alignment with a desired cut, the system is configuredso that the femur target is within the camera's field of view, and thecomputing unit may execute instructions to generate display informationbased on the relative pose of the cutting feature of the saw blade andthe patient anatomy. The computing unit may receive optical signals ofthe femur target from the camera and calculate femur target pose. Thecomputing unit may further calculate the pose of the anatomy withrespect to the camera based on the femur target pose and theregistration of the anatomical axes to the femur target. The computingunit may utilize the pose of the cutting feature and anatomy, each withrespect to the camera, to calculate the pose of the cutting feature withrespect to the anatomy.

The pose of the cutting feature with respect to the anatomy may befurther processed for display. The further processing may include:generating a graphical representation of the pose; expressing the poseaccording to clinically relevant conventions, etc. For example, in TKA,the pose may be expressed as at least any one of: a varus and/or valgusangle; an extension angle and/or flexion angle; a medial resectionlevel; and a lateral resection level. A surgeon may position a cuttingguide based on the display information. Alternatively, a surgeon maymeasure the positional characteristics of a cutting guide fixed to thefemur by receiving display information when the cutting tool is coupledwith the slot of the cutting guide (i.e. to confirm the correct orsatisfactory alignment of the cutting guide).

The display information based on the pose of the cutting feature withrespect to the anatomy may be presented to a user and updated in realtime (or substantially real-time, such as <1 s latency and 30 Hz) by thecomputing unit, responsive to positional changes of the cutting toolwith respect to the anatomy. When used with a robotic system, the poseof the cutting feature with respect to the anatomy may be provided to arobotic controller, instead of being provided for display or may beprovided additionally for such purpose (i.e. and/or). Any systemconfigured to provide the pose for display, provide for a roboticcontroller or both for display and a robotic controller is contemplatedherein. It is intended that a system that is configured to only providethe pose for display or a system that is configured only provide thepose for a robotic controller is also within the scope of the teachingsherein and a system is not required to be configured to provide the posein the alternative for display or to the robotic controller (or for bothsuch purposes). The same applies to method and other aspects.

The system may provide a tibial target, and the computing unit mayexecute further instructions analogous to the femur guidance, but fortibial positional guidance. The surgeon may carry out analogous stepsfor tibial positional guidance.

An oscillating saw blade with application to bone removal in TKA is aprimary example throughout this description; however, this descriptionis not limited to this example. Other types of cutting tools may besubstituted for the oscillating saw blade, including high speed burrs,lasers, drill bits, reciprocating saw blades, rasps, suctions etc.Cutting tools may be provided in sterile packaging configured to hold asterile and single use cutting tool prior to use.

Power tools corresponding to the type of cutting tool may besubstituted. Any type of medical and/or surgical procedure where bony orother tissue is cut, removed or altered by power tools may besubstituted for TKA, for example, total hip arthroplasty, ear nosethroat (ENT) surgery, cranial surgery, unicompartmental knee surgery,high tibial osteotomy, spinal surgery including pedicle screw placement,jaw realignment, etc.

There is provided a computer implemented method to navigate a bone cutof a patient's bone. The computer implemented method may be performed bya system comprising: a cutting tool comprising: a cutting feature; anoptically trackable feature, wherein: the optically trackable feature isdetectable by a camera; and the optically trackable feature has adefined positional relationship with the cutting feature; and aninterface to couple the cutting tool to a power tool; and a computingunit communicatively coupled to the camera, the computing unitcomprising at least one processing unit and a storage device storinginstructions. The instructions, which when executed by the at least oneprocessing unit, may configure the system's computing unit to performthe method. As shown in FIG. 9, a flowchart of operations 900, themethod comprises: at 902 receiving a first image from the camera when:the cutting tool is in a nominal stationary position, the camera isattached to the power tool, and a field of view of the camera includesthe optically trackable feature; at 904 measuring a relative pose of thecamera and the optically trackable feature based on the first image; at906 computing a relative pose of the camera and the cutting featurebased on the defined positional relationship; at 908 receiving a secondimage from the camera when: a target associated with a patient's bone iswithin the field of view of the camera; at 910, measuring a relativepose of the camera and the target based on the second image; at 912,computing a relative pose of the cutting feature with respect to thepatient's bone based on the relative pose of the camera and the targetassociated with the patient's bone and the relative pose of the cameraand the cutting feature; and at 914, providing the relative pose of thecutting feature with respect to the patient's bone to determine displayinformation for display and/or to a robotic controller for controlling aprocedure.

The method may also include performing a registration of a patient'sanatomical axes to the target, and using the registration of thepatient's anatomical axes to the target to compute the relative pose ofthe cutting feature with respect to the patient's bone.

FIG. 10 is a flowchart of operations 1000, showing a method for a TKAprocedure according to an example. Operations 1000 may be performedadditionally to operations 900 in TKA but will be understood to definetheir own method as well. The method may comprise: at 1002 receiving athird image from the camera when a second target associated with apatient's tibia is within the field of view of the camera; at 1004,measuring a relative pose of the camera and the second target based onthe third image; at 1006, computing a relative pose of the cuttingfeature with respect to the patient's tibia based on the relative poseof the camera and the second target and the relative pose of the cameraand the cutting feature; and, at 1008, computing and providing fordisplay at least one of: a varus/valgus angle, a flexion/extensionangle, a lateral resection level, and a medial resection level, based onthe relative pose of the cutting feature with respect to the patient'stibia. The relative pose of the cutting feature with respect to thepatient's tibia may be provided to a robotic controller for controllinga procedure.

FIG. 11 is a flowchart of operations 1100, showing a method fornavigating a bone cut, according to an example. Operations 1100 may beperformed additionally to operations 900 in but will be understood todefine their own method as well. The method comprises: at 1102,continuously receiving image data of the target from the cameracomprising additional images, the target attached to the patient's bone;at 1104, continuously measuring a relative pose of the camera and thetarget based on the additional images; at 1106, continuously computing arelative pose of the cutting feature with respect to the patient's bonebased on the relative pose of the camera and the target associated withthe patient's bone and the relative pose of the camera and the cuttingfeature; and at 1108, continuously providing the relative pose of thecutting feature with respect to the patient's bone to determine displayinformation for real-time display and/or providing to a roboticcontroller for controlling a procedure.

When the term “continuously” is used herein, it will be understood tomean periodically, in real time, such as to give sufficient feedbacke.g. via the display information (e.g. measurements) in response torelative movement of the components (e.g. camera and any bones which aretracked) as previously described or to provide information to a roboticcontroller for controlling a procedure.

It is further understood that various methods described for performanceby a computer system such as navigational surgery may be implemented insoftware such as instructions and data to configure at least oneprocessing unit of a computer system to perform the method. Theinstructions and data may be stored in a device such as a memory (RAM,ROM, flash drive, etc.) or other non-transitory storage device (e.g.:magnetic, optical, or other disk or storage medium).

Accordingly, it is to be understood that this subject matter is notlimited to particular embodiments described, and as such may vary. It isalso to be understood that the terminology used herein is for thepurpose of describing particular embodiments only, and is not intendedto be limiting. As will be apparent to those of skill in the art uponreading this disclosure, each of the individual embodiments describedand illustrated herein has discrete components and features which may bereadily separated from or combined with the features of any of the otherseveral embodiments without departing from the teachings herein. Anyrecited method can be carried out in the order of events recited or inany other order which is logically possible.

The invention claimed is:
 1. A system to navigate a bone cut of apatient's bone comprising: a cutting tool comprising: a cutting feature;an optically trackable feature, wherein: the optically trackable featureis detectable by a camera; and the optically trackable feature has adefined positional relationship with the cutting feature; and aninterface to couple the cutting tool to a power tool; and a computingunit communicatively coupled to the camera, the computing unitcomprising at least one processing unit and a storage device storinginstructions, which when executed by the at least one processing unit,configure the computing unit to: receive a first image from the camerawhen: the cutting tool is in a nominal stationary position, the camerais attached to the power tool, and a field of view of the cameraincludes the optically trackable feature; measure a relative pose of thecamera and the optically trackable feature based on the first image;compute a relative pose of the camera and the cutting feature based onthe defined positional relationship; receive a second image from thecamera when: a target associated with a patient's bone is within thefield of view of the camera; measure a relative pose of the camera andthe target based on the second image; compute a relative pose of thecutting feature with respect to the patient's bone based on the relativepose of the camera and the target associated with the patient's bone andthe relative pose of the camera and the cutting feature; and provide therelative pose of the cutting feature with respect to the patient's bonefor display and/or to a robotic controller for controlling a procedure.2. The system of claim 1 wherein the instructions configure thecomputing unit to perform a registration of a patient's anatomical axesto the target, and to use the registration of the patient's anatomicalaxes to the target to compute the relative pose of the cutting featurewith respect to the patient's bone.
 3. The system of claim 2 wherein thepatient's bone is a femur, the bone cut is a distal femoral cut in aTKA, and the display information includes at least one of: avarus/valgus angle; a flexion/extension angle, a lateral resectionlevel, and a medial resection level with respect to the femur.
 4. Thesystem of claim 3 wherein the instructions configure the computing unitto: receive a third image from the camera when a second targetassociated with a patient's tibia is within the field of view of thecamera; measure a relative pose of the camera and the second targetbased on the third image; compute a relative pose of the cutting featurewith respect to the patient's tibia based on the relative pose of thecamera and the second target and the relative pose of the camera and thecutting feature; and compute and provide for display at least one of: avarus/valgus angle, a flexion/extension angle, a lateral resectionlevel, and a medial resection level, based on the relative pose of thecutting feature with respect to the patient's tibia.
 5. The system ofclaim 1 wherein the cutting tool is one of: an oscillating saw blade, areciprocating saw blade, a drill bit, a high speed burr, and a rasp. 6.The system of claim 1 wherein the cutting tool is an oscillating sawblade, and the optically trackable feature is a pattern of reflectivematerial applied to a recessed surface of the oscillating saw blade. 7.The system of claim 1 wherein the cutting tool is an oscillating sawblade, wherein the optically trackable feature comprises a firstoptically trackable feature and the cutting tool comprises a secondoptically trackable feature identical to the first optically trackablefeature and wherein the first optically trackable feature and secondoptically trackable feature appear on opposite sides of the oscillatingsaw blade.
 8. The system of claim 1 wherein the cutting tool has aprimary plane or axis, and the defined positional relationship is basedon the optically trackable feature lying along the primary plane oraxis.
 9. The system of claim 1 wherein the camera is integrated into thepower tool.
 10. The system of claim 1 wherein the instructions configurethe computing unit to: continuously receive image data of the targetfrom the camera comprising additional images, the target attached to thepatient's bone; continuously measure a relative pose of the camera andthe target based on the additional images; continuously compute arelative pose of the cutting feature with respect to the patient's bonebased on the relative pose of the camera and the target associated withthe patient's bone and the relative pose of the camera and the cuttingfeature; and continuously provide the relative pose of the cuttingfeature with respect to the patient's bone to determine displayinformation for real-time display and/or to a robotic controller forcontrolling a procedure.